✨ ベストアンサー ✨
(1) This school has (many books, most of which were brought) from the children's homes.
← This school has many books, and most of them(=the books) were brought from the children's homes.
(2) Ken made (supper for the children, most of whom were) street children.
← Ken made supper for the children, and most of them(=the children) were street children.
(3) About 100 young people, (half of whom are from abroad), are working on this farm.
← About 100 young people, and half of them(=the young people) are from abroad, are working on this farm.
参考にしてください。